The present invention relates to a safety switch.
In a variety of environments, including for example industrial environments, there is a need for systems that are capable of preventing access to one or more pieces of equipment or machinery whilst that equipment or machinery is operating, in a manner that is highly reliable. In some instances this may be achieved by connecting a safety switch to a control system.
Known control systems are designed to disconnect, ground and otherwise isolate controlled equipment/machinery from one or more power sources in a predictable, reliable manner, for example upon actuation of a safety switch. Such control systems reduce the chance that the controlled equipment/machinery might be unintentionally restarted at a time when it is being accessed by repair personnel or technicians for purposes or repair or modification, and thereby enhance the confidence and rapidity with which such personnel can accomplish such repairs/modifications. The power sources from which the controlled equipment/machinery are isolated by these control systems can include any of a number of power sources including, for example, electrical, pneumatic and hydraulic power sources.
Referring to FIG. 1, one prior art control system of this type is the ElectroGuard™ Bulletin 2030 Safety Isolation System available from Rockwell Automation, Inc. of Milwaukee, Wis. This control system, shown in FIG. 1 as a control system 2, includes both an electric power isolation system 4 and a pneumatic (or hydraulic) power isolation system 6, and operates as follows.
When a failure or other condition occurs at a machine 8 of an industrial system 10 (in this case, an assembly line), and an operator appropriately switches or triggers a remote lockout switch (RLS) 12 associated with that machine to an “OFF” position, the control system 2 serves to disconnect both electric power and pneumatic power lines 15 and 16, respectively, from the machine so as to as decouple the machine from both of those types of power. Additionally, the control system 2 then further serves to ground the machine 8.
Once the machine 8 has been isolated in this manner, an indication is provided to the operator (e.g. a light 18 turns on) indicating that it is appropriate for the operator to access the machine for purposes of making a repair or some other modification to the machine. Typically, the operator will then access the machine by entering into a normally-inaccessible region, e.g., by opening a gate 20 and entering into the machine as shown (alternatively, for example the operator could pass through a light curtain).
Once the operator has completed repair/modification and left the normally-inaccessible region, the operator appropriately switches or triggers the RLS 12 again, this time to an “ON” position. After this occurs, the control system 2 re-establishes the connections between the power sources and the machine 8. The control system 2 typically employs redundant circuitry such as safety relays to enhance the control system's reliability in performing its control functions in this regard.
It is an object of the present invention to provide a safety switch which may be coupled with a control system to restrict access to equipment/machinery.